Control valve

ABSTRACT

A control valve, particularly for a device for altering the actuation periods of an internal combustion engine, which has a valve housing that is configured with a substantially hollow cylindrical structure, a control piston disposed inside the valve housing and is axially displaceable therein, and a closing element. The control piston has at least one section with a hollow structure that ends in an opening of the control piston and the closing element is disposed in the opening.

FIELD OF THE INVENTION

The invention relates to a control valve, in particular for a device for varying the control times of an internal combustion engine, with an essentially hollow-cylindrically designed valve housing, an axially displaceable control piston arranged inside the valve housing, and a closing element, the control piston having at least one portion of hollow design which issues into an orifice of the control piston, and the closing element being arranged in the orifice.

The invention relates, further, to a method for producing a control valve, in particular for a device for varying the control times of an internal combustion engine, with an essentially hollow-cylindrically designed valve housing, an axially displaceable control piston arranged inside the valve housing, and a closing element, the control piston having at least one portion of hollow design which issues into an orifice of the control piston.

Control valves of this type are used in order to control pressure medium streams in hydraulic devices, for example hydraulic devices for varying the control times of an internal combustion engine (camshaft adjusters).

A control valve of this type and a camshaft adjuster are known, for example, from DE 10 2004 038 252 A1. The camshaft adjuster has two components rotatable in relation to one another and two pressure chambers acting counter to one another, the relative phase of the two components being capable of being selectively varied or changed by the pressure chambers being loaded with or relieved of pressure in a directed manner.

The control of the pressure medium streams to and from the pressure chambers takes place by means of a control valve, in this case a 4/3-way proportional valve. Other types of directional valves may also be envisaged, however, in particular with different numbers of connections and/or control positions.

The control valve consists essentially of an electromagnetic actuating drive, of a hollow-cylindrically designed valve housing and of a likewise essentially hollow-cylindrically designed axially displaceable control piston arranged inside the valve housing. The valve housing is provided in each case with a connection for the pressure chambers (working connection), with a connection to the pressure medium pump and with at least one connection to a tank.

The control piston can be brought axially into any position between two defined end positions, counter to the spring force of a spring element, by means of an electromagnetic actuating member. The control piston is provided, furthermore, with annular grooves and control edges, with the result that the individual pressure chambers can be connected selectively to the pressure medium pump or to the tank. A position of the control piston may likewise be provided in which the pressure medium chambers are separated both from the pressure medium pump and from the pressure medium tank.

The control piston can be displaced into any desired position inside the valve housing by means of the actuating drive which acts counter to a spring element. For this purpose, an axial orifice of the control piston, which stands opposite the actuating drive, is closed, tight to pressure medium, by means of a closing element. A tappet rod movable linearly by the actuating drive, acts on this closing element. The closing element is connected to the control piston by means of a nonpositive connection, for example by the closing element being pressed with oversize into the orifice of the control piston.

In modern internal combustion engines, high alternating moments act upon the camshafts on account of the opening and closing movement of the gas exchange valves counter to the force of a valve spring. These alternating moments generate in the camshaft adjusters pressure peaks which may exceed 100 bar. These pressure peaks are transmitted to the control valve via the hydraulic system. There may then be the risk that, in the presence of high alternating moments and therefore high pressure peaks, the axial securing of the closing element in relation to the control piston is canceled and, for example, the closing element creeps out of the orifice.

The result of this, on the one hand, may be that the full valve stroke of the control valve can no longer be utilized, the consequence of this being that the performance, in particular the adjustment speed, that camshaft adjusters is significantly impaired.

On the other hand, the cancellation of the fixed axial relation of the closing element to the control piston leads to a situation where, in a specific position of the tappet rod, the expected position of the control piston in relation to the valve housing is not identical to the actual position, with the result that the regulation of the camshaft adjuster is seriously disrupted.

SUMMARY OF THE INVENTION

The object on which the invention is based, therefore, is to avoid these outlined disadvantages and therefore to provide a hydraulic control valve, in which, in particular, a deterioration in the performance and regulating accuracy of the control valve during operation is to be prevented.

In a first embodiment, this object is achieved, according to the invention, in that the closing element has a circumferential wall which is adapted essentially to an inner surface area of the control piston in the region of the orifice, the circumferential wall having at least one material receptacle of smaller outside diameter, the material receptacle being followed in the axial direction of the closing element by a region of larger outside diameter on the side facing away from the orifice, and the inner surface area of the control piston engaging into the material receptacle.

In this case, there may be provision for the material receptacle to be designed as an annular groove proceeding in the circumferential direction of the closing element. Alternatively, the material receptacle may be designed as a pocket. Embodiments may likewise be envisaged in which the material receptacle is designed as a chamfer of a circumferential edge of an axial sidewall of the closing element.

In a development of the invention, there is provision for the outside diameter of the control piston to be made smaller in the region of the material receptacle than a maximum outside diameter of the control piston.

In addition, there may be provision for connecting the closing element (37 b) to the control piston (37) by means of a materially integral connection, an adhesive bond, a soldered joint or a welded joint.

In a further embodiment, the object is achieved, according to the invention, in that the closing element is connected to the control piston by means of a materially integral connection, an adhesive bond, a soldered joint or a welded joint.

The object is by means of a method according to the invention having the following steps:

-   -   positioning of the closing element inside the orifice of the         control piston,     -   displacement of material of the control piston radially inward         in the region of the closing element,     -   solved.

In this case, there may be provision for the material of the control piston to be displaced radially inward by means of radial embossing, radial circumferential calking or radial segmental calking of the control piston.

Alternatively, there may be provision for the material of the control piston to be displaced radially inward by means of axial embossing, axial annular calking or axial segmental calking of an axial side face of the control piston.

In a development of the method according to the invention, there may be provision for the material to be displaced into at least one material receptacle formed on a circumferential face of the closing element.

In a control valve of this type, a control piston is arranged axially displaceably inside an essentially hollow-cylindrically designed valve housing. The control piston is of hollow design at least in one portion, this portion ending in an orifice of the control piston. In this case, there may be provision for the orifice to be formed on an axial side face of the control piston.

In addition to this orifice, further orifices, in particular radial bores, may be provided, via which the portion of hollow design of the control piston communicates, for example, with a pressure medium pump or with working connections or, via these, with a consumer.

The control piston may, for example, be designed as an essentially hollow-cylindrical structural element or may have a U-shaped design in longitudinal section.

A closing element is arranged inside the orifice. The closing element may, for example, be of cylindrical or pot-shaped design and serve, for example, for closing the orifice tight to pressure medium. Furthermore, there may be provision for the closing element to serve as a bearing element for a tappet rod, via which an actuating movement of an actuating member can be transmitted to the control piston.

In this case, there is provision for the radially outer circumferential wall of the closing element to be adapted to an inner surface area of the control piston in the region of the orifice.

In order to increase the press-out forces of the closing element, there may be provision, on the one hand, for making a nonpositive connection between the closing element and the control element. This may be implemented, for example, by pressing the closing element designed with oversize into the orifice. In order to increase the nonpositive connection, there may be provision for displacing material of the control piston radially inward after the positioning of the closing element inside the orifice. This may be implemented, for example, by means of the radial embossing, radial circumferential calking or radial segmental calking or by means of the axial embossing, axial annular calking or axial segmental calking of an axial side face of the control piston radially inward.

Additionally or alternatively to this, there may be provision for the circumferential wall of the closing element to have at least one material receptacle of smaller outside diameter, the inner surface area of the control piston engaging into the material receptacle. In this case, the material receptacle may be followed in the axial direction by a region of the closing element, the outside diameter of which is designed to be larger than the outside diameter in the region of the material receptacle. Thus, a positive connection is achieved, and the closing element is effectively prevented from creeping. In the event that the material receptacle is followed by the region of enlarged diameter on the side facing away from the orifice, this prevents the closing element from creeping out of the control piston. With an opposite configuration, a creeping of the closing element into the control piston, for example due to the action of force by a tappet rod acting on the closing element, can be prevented. It is likewise conceivable that the material receptacle is followed on both sides by regions of enlarged diameter, with the result that the closing element is secured in position by means of a positive connection.

Additionally or alternatively to the abovementioned solutions, a materially integral connection, an adhesive bond, a soldered joint or a welded joint may be provided between the closing element and the control piston.

While the material displacement is being carried out on the control piston, material build-ups may occur on the outer surface area of the control piston due to the engagement of tools. These build-ups, if they project beyond the maximum outside diameter of the control piston, may lead to a jamming of the control piston inside the valve housing. This is effectively counteracted by the control piston being designed in the region of the material receptacle with a smaller outside diameter than the maximum outside diameter of the control piston. Furthermore, the annular wall portion generated thereby at the interface between the regions of different outside diameter may be utilized as a stop for the material displacement tool.

The material displacements may take place along the entire circumference of the control piston or only segmentally.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the invention may be gathered from the following description and from the drawings which illustrate exemplary embodiments of the invention in a simplified form and in which:

FIG. 1 shows a longitudinal section through a device for varying the control times of an internal combustion engine, together with a pressure medium circuit;

FIG. 2 shows a cross section through the device illustrated in FIG. 1;

FIG. 3 shows a longitudinal section through a control valve according to the invention;

FIG. 4 a shows a longitudinal section through a first embodiment of a control piston of a control valve according to the invention;

FIG. 4 b shows a perspective view of the control piston from FIG. 4 a;

FIG. 5 a shows a cross section through a second embodiment of a control piston of a control valve according to the invention; and

FIG. 5 b shows a longitudinal section through the control piston from FIG. 5 a along the line A-A.

DETAILED DESCRIPTION OF THE DRAWING

FIGS. 1 and 2 show a device 1 for varying the control times of an internal combustion engine. The device 1 consists essentially of a stator 2 and of a rotor 3 arranged concentrically thereto. A drive wheel 4 is connected fixedly in terms of rotation to the stator 2 and, in the embodiment illustrated, is designed as a chain wheel. The stator 2 is mounted rotatably on the rotor 3, in the embodiment illustrated five recesses 5 spaced apart in the circumferential direction being provided on the inner surface area of the stator 2. The recesses 5 are delimited in the radial direction by the stator 2 and the rotor 3, in the circumferential direction by two sidewalls 6 of the stator 2 and in the axial direction by a first and a second side cover 7, 8. Each of the recesses 5 is closed, pressure-tight, in this way.

Vane grooves 10 proceeding axially are formed on the outer surface area of the rotor 3, a radially extending vane 11 being arranged in each vane groove 10. A vane 11 extends into each recess 5, the vanes 11 bearing in the radial direction against the stator 2 and in the axial direction against the side covers 7, 8. Each vane 11 subdivides a recess 5 into two pressure chambers 12, 13 acting counter to one another.

By means of first and second pressure medium lines 16, 17, the first and second pressure chambers 12, 13 can be connected via a control valve 18 to a pressure medium pump 19 or to a tank 20. An actuating drive is thereby formed which allows a relative rotation of the stator 2 with respect to the rotor 3. When the first pressure chambers 12 are connected to the pressure medium pump 19 and the second pressure chambers 13 to the tank 20, the first pressure chambers 12 expand at the expense of the second pressure chambers 13. This results in a displacement of the vanes 11 in a circumferential direction, in the direction illustrated by the arrow 21. As a result of the displacement of the vanes 11, the rotor 3 is rotated with respect to the stator 2.

The relative rotation of the rotor 3 with respect to the stator 2 results in a phase displacement between the camshaft and crankshaft as a consequence of the supply or discharge of pressure medium to or from the pressure chambers 12, 13. By pressure medium being introduced into or discharged from the pressure chambers 12, 13 in a directed manner, the control times of the gas exchange valves of the internal combustion engine can thus be varied or selectively held in a directed way.

In the embodiment illustrated, the pressure medium lines 16, 17 are designed as essentially radially arranged bores which extend from a central bore 22 of the rotor 3 to the outer surface area of the latter. Inside the central bore 22, a central valve, not illustrated, may be arranged, via which the pressure chambers 12, 13 can be connected to the pressure medium pump 19 or to the tank 20 in a directed manner. A further possibility is to arrange inside the central bore 22 a pressure medium distributor which connects the pressure medium lines 16, 17 to the connections of an externally mounted control valve 18 via pressure medium ducts and annular grooves.

FIG. 3 illustrates a control valve 18 according to the invention in longitudinal section. An essentially hollow-cylindrically designed valve housing 34 is designed with a radial pressure medium connection P, with a radial tank connection T₁, with two working connections A, B and with an axial tank connection T₂. The radial connections P, T₁, A, B are designed as first annular grooves 35 which are spaced axially apart from one another and which are formed on the outer surface area of the valve housing 34. The first annular grooves 35 are provided with a plurality of first bores 36 which issue into the interior of the valve housing 34.

A likewise essentially hollow-cylindrically designed control piston 37 is arranged axially displaceably inside the valve housing 34. One axial end of the control piston 37 is delimited, pressure-tight, by means of a wall portion 37 a. A closing element 39 is arranged in an orifice 37 b, lying opposite the wall portion 37 a, of the control piston 37. The closing element 39 is designed in such a way that it closes the orifice 37 b pressure-tight.

By means of an actuating member 32, the control piston 37 can be brought into and held in any desired position within two extreme values, counter to the spring force of a spring element 33, by means of a tappet rod 32 a. For this purpose, the tappet rod 32 a of the actuating member 32 bears against the closing element 39. Linear actuating movements of the actuating member 32 are thus transmitted via the tappet rod 32 a to the closing element 39 and therefore to the control piston 37.

The outer surface area of the control piston 37 is provided with three axially spaced-apart second annular grooves 38. The two outer annular grooves 38 communicate via second bores 41 with the interior of the control piston 37. Via the annular grooves 38, the second bores 41 and the interior of the control piston 37, pressure medium can be conducted from the pressure medium connection P to the first or second working connections A, B as a function of the position of the control piston 37 inside the valve housing 34, the interior of the control piston 37 being connected to the pressure medium connection P in any position. Likewise, in the case of specific positions of the control piston 37 in relation to the valve housing 34, pressure medium can pass from the second working connection B via the middle annular groove 38 to the radial tank connection T₁ and from the first working connection A to the axial tank connection T₂.

Thus, by the position of the control piston 37 inside the valve housing 34 being influenced in a directed manner, pressure medium can be conducted to specific pressure chambers 12, 13 and be discharged from the other pressure chambers 12, 13, thus leading to a relative change in the phase position between the rotor 3 and stator 2 and, consequently, between the crankshaft and camshaft.

Due to the pressure prevailing inside the control piston 37, there may be the risk that the closing element 39 creeps in the axial direction. This risk is due, above all, to the alternating moments acting on the camshaft and caused by the gas exchange valve springs, with the result that pressures above 100 bar may be induced in the hydraulic system. In order to prevent the closing element 39 from creeping, in the embodiments according to the invention of a control valve 18, the connection between the control piston 37 and the closing element 39 is to be strengthened. This may be achieved, for example, by means of a positive and/or materially integral connection and/or a strengthening of the nonpositive connection. Adhesive bonds or combinations of these types of connection may likewise be envisaged.

FIGS. 4 a and 4 b show a first embodiment according to the invention of a control piston 37.

In this embodiment, the closing element 39 is of pot-shaped design, a cylindrical circumferential wall 39 a of the closing element 39 coming to bear against the inner surface area 37 d of the orifice 37 b. After the operation of pressing the closing element 39 into the orifice 37 b of the control piston 37, material 37 c of the control piston 37 is displaced radially inward in the region of the cylindrical circumferential wall 39 a. This may take place, for example, by means of radial embossing or calking. In this case, the material displacement may take place along the entire circumference of the control piston 37 in the form of an annular groove or segmentally, as illustrated in the embodiment. This leads to a reinforcement of the nonpositive connection between the control piston 37 and closing element 39.

Additionally, so that the flowing material can be received on the inner surface area 37 d of the control piston 37, there may be provision for forming on the closing element 39 one or more material receptacles 40, for example circumferential grooves or pockets, into which the material 37 c can be displaced. This gives rise to a positive connection between the control piston 37 and the closing element 39, with the result that the press-out forces are increased significantly.

During the material displacement operation, the outside diameter of the control piston 37 may become slightly larger at the margins of the pressure-loaded region. In order to prevent this enlargement in diameter from leading to a jamming of the control piston 37 inside the valve housing 34, there is provision for making the outside diameter of the control piston 37 smaller in the region of the material displacement than the maximum outside diameter of the control piston 37, in particular smaller than the inside diameter of the valve housing 34.

FIGS. 5 a and 5 b show a second embodiment according to the invention of a control piston 37. In this exemplary embodiment, too, after the closing element 39 has been positioned inside the control piston 37, for example by means of an operation to press the closing element 39 with oversize into the orifice 37 b of the control piston 37, material 37 c of the control piston 37 is displaced radially inward. In contrast to the first embodiment, this takes place by axial embossing by means of annular or segmental calking. In this case, the tool is pressed into the axial side face (annular wall 37 e) of the control piston 37. As a result, the nonpositive connection between the closing element 39 and the control piston 37 is increased, and a positive connection occurs in the creeping direction, and therefore the relative position of the closing element 39 with respect to the control piston 37 is secured.

In order to absorb the material build-up which occurs, material receptacles 40 may be provided here, too. In the exemplary embodiment, the material receptacle 40 is implemented by means of a suitably dimensioned phase 40 a or a suitably dimensioned radius of the orifice-side bottom of the closing element 39. In this case, both the chamfer 40 a and the material displacement may extend over the entire outer circumference of the bottom or may be formed only segmentally.

Alternatively to the pot-shaped embodiment of the closing element 39, as illustrated, other embodiments, for example a cylindrical closing element 39, may be provided.

Alternatively, there may be provision for connecting the closing element 39 to the control piston 37 by means of an adhesive bond or a soldered or welded joint. Combinations of the first and the second embodiment with an adhesive bond or soldered or welded joint may likewise be envisaged.

REFERENCE SYMBOLS

-   1 Device -   2 Stator -   3 Rotor -   4 Drive wheel -   5 Recesses -   6 Sidewall -   7 First side cover -   8 Second side cover -   10 Vane groove -   11 Vane -   12 First pressure chamber -   13 Second pressure chamber -   16 First pressure medium line -   17 Second pressure medium line -   18 Control valve -   19 Pressure medium pump -   20 Tank -   21 Arrow -   22 Central bore -   31 Pressure medium circuit -   32 Actuating member -   32 a Tappet rod -   33 Spring element -   34 Valve housing -   35 First annular groove -   36 First bores -   37 Control piston -   37 a Wall portion -   37 b Orifice -   37 c Material -   37 d Inner surface area -   37 e Annular wall -   38 Second annular groove -   39 Closing element -   39 a Circumferential wall -   40 Material receptacle -   40 a Chamfer -   41 Second bore -   P Pressure medium connection -   T₁ Radial tank connection -   T₂ Axial tank connection -   A First working connection 

1. A control valve for a device for varying the control times of an internal combustion engine, comprising: an essentially hollow-cylindrically designed valve housing; an axially displaceable control piston arranged inside the valve housing; and a closing element, the control piston having at least one portion of hollow design which issues into an orifice of the control piston, and the closing element being arranged in the orifice, wherein the closing element has a circumferential wall which is adapted essentially to an inner surface area of the control piston in a region of the orifice, the circumferential wall having at least one material receptacle of smaller outside diameter, the material receptacle being followed in an axial direction of the closing element by a region of larger outside diameter on a side facing away from the orifice, and the inner surface area of the control piston engaging into the material receptacle.
 2. The control valve of claim 1, wherein the material receptacle an annular groove proceeding in a circumferential direction of the closing element.
 3. The control valve of claim 1, wherein the material receptacle is a pocket.
 4. The control valve of claim 1, wherein the material receptacle is a chamfer of a circumferential edge of an axial sidewall of the closing element.
 5. The control valve of claim 1, wherein the outside diameter of the control piston is made smaller in the region of the material receptacle than a maximum outside diameter of the control piston.
 6. The control valve of claim 1, wherein the closing element is connected to the control piston by means of a materially integral connection, an adhesive bond, a soldered joint or a welded joint.
 7. A control valve for a device for varying control times of an internal combustion engine, comprising: an essentially hollow-cylindrically designed valve housing; an axially displaceable control piston arranged inside the valve housing; and a closing element, the control piston having at least one portion of hollow design which issues into an orifice of the control piston, and the closing element being arranged in the orifice, wherein the closing element is connected to the control piston by means of a materially integral connection, an adhesive bond, a soldered joint or a welded joint.
 8. A method for producing a control valve for a device for varying control times of an internal combustion engine, comprising: an essentially hollow-cylindrically designed valve housing; an axially displaceable control piston arranged inside the valve housing; and a closing element, the control piston having at least one portion of hollow design which issues into an orifice of the control piston, having the following steps: positioning of the closing element inside the orifice of the control piston, and displacement of material of the control piston radially inward in the region of the closing element.
 9. The method of claim 8, wherein the material of the control piston is displaced radially inward by means of radial embossing, radial circumferential calking or radial segmental calking of the control piston.
 10. The method of claim 8, wherein the material of the control piston is displaced radially inward by means of axial embossing, axial annular calking or axial segmental calking of an axial side face of the control piston.
 11. The method of claim 8, wherein the material is displaced into at least one material receptacle formed on a circumferential face of the closing element. 